Interpretive Summary: Most Crotalaria species are weedy but a few have been used as a crop with agricultural, economic and pharmaceutical importance. They can be used as cover crops for providing green manure and preventing soil erosion, as rotation crops for nitrogen fixation, as forage crops for grazing, as a source of long fiber to produce high quality paper, as intercepting crops for nematode control, and as medicinal plants for chemical compound extraction. Sunn hemp (Crotalaria juncea L.) is one of the main species in the genus and grown worldwide in tropical areas. In this book chapter, we focused on sunn hemp, describing its basic botany and discussing its conservation activity, classical genetics, breeding improvement and multiple utilizations, and also pointing out the future actions.

Technical Abstract:
The genus Crotalaria has about 600 species distributed mostly in tropical and subtropical areas of the southern hemisphere and Africa. Most Crotalaria species are weedy but a few have been used as a crop with agricultural, economic and pharmaceutical importance. They can be used as cover crops for providing green manure and preventing soil erosion, as rotation crops for nitrogen fixation, as forage crops for grazing, as a source of long fiber to produce high quality paper, as intercepting crops for nematode control, and as medicinal plants for chemical compound extraction. Sunn hemp (Crotalaria juncea L.) is one of the main species in the genus and grown worldwide in tropical areas. In this book chapter, we focused on sunn hemp, describing its basic botany and discussing its conservation activity, classical genetics, breeding improvement and multiple utilizations, and also recommending the future actions. The future actions include: (1) Expanding the germplasm stored in banks; (2) Generation of genomic resources; (3) Generation of genetic resources; (4) Breeding for photoperiod insensitivity; (5) Biochemical and biological analysis; and (6) Further exploiting of its utilization.